System for ultrasonically detecting the relative position of a moveable device

• US 4,543,649 A
• Filed: 10/17/1983
• Issued: 09/24/1985
• Est. Priority Date: 10/17/1983
• Status: Expired due to Fees

• Current Assignee: High-Kim Investment Corporation
• Original Assignee: Teknar Incorporated
• Inventors: Bollinger, Arthur E., Head, Kenneth O.
• Primary Examiner(s): Farley, Richard A.
• Application Number:
  US06/542,696
• Time in Patent Office: 708 Days
• Field of Search: 01S/15/88, 01S/7/52, 367/13, 367/95, 367/96, 367/99, 367/108, 367/902, 367/908, 73/703
• US Class Current: 367/96
• CPC Class Codes: B60G 17/01933 Velocity, e.g. relative velocity-displacement sensors
• CPC Class Codes: B60G 2202/41 Fluid actuator
• CPC Class Codes: B60G 2204/112 on dampers, e.g. fluid dampers
• CPC Class Codes: B60G 2400/25 Stroke; Height; Displacement
• CPC Class Codes: B60G 2401/15 Doppler effect
• CPC Class Codes: B60G 2401/176 Radio or audio sensitive means, e.g. Ultrasonic
• CPC Class Codes: G01S 15/88 Sonar systems specially adapted for specific applications seismic or acoustic prospecting or detecting G01V1/00
• CPC Class Codes: G01S 2007/52014 involving a reference reflector integrated in the sensor or transducer configuration
• CPC Class Codes: G01S 7/52006 with provision for compensating the effects of temperature
• CPC Class Codes: Y10S 367/902 Speed of sound compensation

Abstract

An ultrasonic system is responsive to the relative position of a movable device within a fluid-filled structure. A transducer transmits ultrasonic signals from a location fixed within the structure to the device for reflection thereby and for picking up the reflected signals. A reference target within the fluid, attached either to the structure or the device, also reflects the transmitted ultrasonic signals from also being picked up by the transducer, such reference target being a predetermined fixed distance relative to either the device or the structure, whereby the different picked up signals reflected from the device and reference target will have a timed relationship corresponding to such fixed distance, measurement circuitry means is responsive to the picked up signals reflected from the device and to such timed relationship for providing an output signal which is a function of change in the position of the device within the structure, being includes circuitry responsive to the timed relationship for causing the output signal to be compensated for changes in the velocity of ultrasonic signals in the fluid resulting from changes in parameters thereof subject to causing errors in the output signal. The structure is, for example, a fluid cylinder and the movable device is a piston within the cylinder. Alternatively, sensing of the parameter is used for output signal compensation.

Claims

1. For use with a fluid cylinder, an ultrasonic system for accurately detecting the relative position of a piston moveable within the fluid cylinder, said system comprising the piston having a surface for reflecting ultrasonic signals, and a reference target within the cylinder for also reflecting ultransonic signals, an ultrasonic transducer for transmitting ultrasonic signals from a location fixed within the structure both to the piston and to the reference target for reflection thereby and for picking up the reflected ultrasonic signals, circuit means responsive to a first time interval between the transmitted and picked up signals for generating an electrical output signal which is a function of the position of the piston within the structure relative to the transducer, said circuit means also being responsive to a further time interval between the transmitted signals and those picked up after reflection by the reference target, and means for causing the output signal to be corrected as a function of the ratio between the first and further time intervals and correcting means including a microprocessor for causing the output signal to be corrected as a function of at least one parameter characteristic of said fluid which is subject to change causing error of the output signal.

2. An ultrasonic system as set forth in claim 1 wherein said reference target is constituted by a thin elongated member extending laterally into the path of said transmitted ultrasonic signals and carried by the structure.

3. An ultrasonic system as set forth in claim 1 wherein the reference target is carried by the piston and constitutes a dimensionally-reduced extension of the piston extending toward the transducer.

4. An ultrasonic system as set forth in claim 1 wherein said correction means comprises a random access memory for storage, under control of said microprocessor, of said first and further time intervals, said microprocessor being configured for utilizing said stored time intervals as a scaling factor for correction of said output signal.

5. An ultrasonic system as set forth in claim 1, wherein said piston is shiftable longitudinally within the fluid cylinder, the output signal being a function of the position of the piston and thereby of the operation of the positioning mechanisms and feedback means for controlling the positioning mechanism as a function of the output signal.

6. An ultrasonic system for accurately detecting the relative position of a moveable device within a fluid-filled structure containing said device, said system comprising an ultrasonic transducer for transmitting ultrasonic signals from a location fixed within the structure to the device for reflection thereby and for picking up the reflected ultrasonic signals, circuit means responsive to a first time interval between the transmitted and signals picked up by reflection from the devices for generating an electrical output signal which is a function of the position of the device within the structure relative to the transducer, and correcting means including a microprocessor for causing the output signal to be corrected as a function of at least one parameter characteristic of said fluid which is subject to change causing error of the output signal, said correction means including a microprocessor and a reference target within the structure for reflecting ultrasonic signals to the transducer to provide predetermined relative distance correlation with signals reflected from the device, said circuit means also being responsive to a further time interval between the transmitted signals and those picked up after reflection by the reference target, the microprocessor comparing the different signals picked up from the device and reference targetr for compensating for changes in velocity of sound in the fluid caused by change in said parameter by causing the output signal to be corrected as a function of the ratio between the first and further time intervals, and a parameter sensing device in said structure for sensing the magnitude of at least one such parameter, electronic data storage means accessible by the microprocessor for correlating the sensed parameter with a further parameter of said fluid, the microprocessor being operative to provide a first output which constitutes said output signal and a further parameter.

7. An ultrasonic system for accurately detecting the relative position of a piston moveable within a fluid cylinder, said system comprising an ultrasonic transducer for transmitting ultrasonic signals from one end of the cylinder to the piston for reflection thereby and for picking up the reflected ultrasonic signals, circuit means responsive to a first time interval between the transmitted and signals picked up by reflection from the device for generating an electrical output signal which is a function of the position of the piston within the cylinder relative to the transducer, and correcting means including a microprocessor for causing the output signal to be corrected as a function of at least one parameter characteristic of said fluid which is subject to change causing error of the output signal, pressure in the fluid being such a parameter, the correcting means comprising a pressure sensor for sensing fluid pressure in the cylinder.

8. An ultrasonic system as set forth in claim 7 wherein the sensing means comprises also a temperature sensor for sensing fluid temperature in the cylinder, and means for comparing the sensed pressure and temperature with electronically stored pressure or temperature data determining correction factors for correction of the output signal.